Cavity Wall Insulation Grant Ireland 2026: Up to €2,300 from SEAI

Cavity Wall Insulation Grant Ireland 2026: What You Need to Know

The SEAI cavity wall insulation grant is one of the most cost-effective grants available in 2026. The installation is fast, the disruption is minimal and the grant now covers a large portion of the total cost for most homes.

Grants for cavity wall insulation increased from 3 February 2026 as part of the Government's National Residential Retrofit Plan, the most generous home energy grant package Ireland has ever offered.

This guide covers who qualifies, what the grant pays, what the installation involves and the strategic reason to do cavity walls before almost any other upgrade.

Do You Have a Cavity Wall? How to Check

Before anything else, you need to know whether your home has a cavity wall.

A cavity wall is made up of two separate layers of masonry with a gap between them. The outer leaf is usually brick or block. The inner leaf is usually block. The gap between them is typically 50mm to 100mm wide. Cavity wall insulation fills that gap.

Homes that typically have cavity walls: Most Irish homes built between 1940 and 2006. This covers the majority of the Irish housing stock, including most 1960s, 1970s, 1980s and 1990s semi-detached and detached houses.

Homes that typically do not have cavity walls: Pre-1940 homes built with solid stone or brick walls. These have no gap to fill. External or internal wall insulation is the route for solid-wall homes. Post-2006 new builds typically already have insulation installed in the cavity and do not need this grant.

How to check before calling a contractor: Look at your external walls. If they are made of brick in a stretcher bond pattern (all bricks lying lengthways), your home probably has a cavity. If you see bricks laid alternating lengthways and sideways (header bond), the wall is likely solid. If your walls are rendered (plastered on the outside), you cannot tell from looking and will need the cavity survey.

Grant Amounts by House Type

Cavity wall insulation grants were increased from 3 February 2026.

Standard Rate

Property type	Standard grant
Detached house	€1,800
Semi-detached or end-of-terrace	€1,200
Mid-terrace	€800
Apartment	€700

Enhanced Rate (qualifying welfare recipients)

From 2 March 2026, homeowners in receipt of qualifying welfare payments receive a flat enhanced rate of €2,300 regardless of property type.

Qualifying payments include: Fuel Allowance, Disability Allowance, Blind Pension, Invalidity Pension, Jobseeker's Allowance (long-term), One-Parent Family Payment, Widow or Widower's Pension, Working Family Payment, Carer's Allowance and Domiciliary Care Allowance.

SEAI verifies welfare eligibility directly with the Department of Social Protection. If you are unsure whether you qualify, apply at the standard rate. If SEAI confirms your payment, the enhanced rate is applied automatically.

For attic and cavity wall insulation, SEAI estimates the grant now covers approximately 80% of the average cost. For many homes on the welfare enhanced rate, the grant covers the full cost of installation.

Who Qualifies

You must meet all of the following:

Your home was built and occupied before 31 December 2010. The cavity wall insulation grant is available to homes built before 2011. Post-2010 homes are typically already insulated during construction and do not qualify.

You are the owner of the property. Owner-occupiers and landlords both qualify. The property owner must submit the application.

Your home has a suitable cavity. Not every home with a cavity wall is suitable for insulation. The cavity must be the correct width, free of debris, not showing signs of damp penetration, and have intact wall ties. The cavity survey confirms this before you apply.

You have not previously claimed this grant on this property. If you or a previous owner has already claimed this grant for the property, you cannot claim again. However, from March 2026 a second wall measure is now available in certain circumstances. See the section below.

Solid-wall homes do not qualify. Stone or brick solid-wall homes are not eligible for this specific grant. If your home is pre-1940 solid masonry, external wall insulation or internal wall insulation are the routes available to you.

The Cavity Survey: What Happens and What It Costs

Your installer checks whether the cavity is suitable, checking for correct width, no major defects and no risk of damp penetration. This is usually free and done before you apply.

Here is what to expect during the survey.

The installer drills a small inspection hole (12mm to 18mm) in the outer leaf of the wall, usually in an inconspicuous spot. They insert a borescope camera into the cavity. The camera shows cavity width, the condition of wall ties, any debris and any signs of moisture.

The survey takes 30 to 60 minutes for a typical semi-D. It covers all external walls. In most cases, it is carried out free of charge by the SEAI-registered installer before they submit a quotation.

If the cavity is suitable, the installer quotes and you apply for the grant. If the cavity is not suitable, they tell you before you spend anything.

Reasons a cavity may be unsuitable include: cavity is too narrow (under 50mm), existing debris making full fill impossible, moisture already present in the cavity, or wall ties in poor condition. In these cases, the installer advises on the best alternative.

Apartments typically require approval from the owners management company (OMC) before works can proceed. Factor this in early.

What Goes Into the Cavity: Three Material Options

Most competitor pages do not explain what cavity wall insulation is actually made of. There are three main materials used by SEAI-registered contractors in Ireland.

EPS bead (expanded polystyrene): The most common material for Irish homes. Small polystyrene beads are injected into the cavity mixed with a bonding adhesive. EPS bead suits cavities from 50mm wide. It fills around obstacles like wall ties and pipe work. It is moisture resistant and does not settle over time.

Mineral wool (glass or rock wool): Blown into the cavity as loose fibres. Better suited to wider cavities. Higher fire resistance than EPS bead. More commonly used in homes with a wider cavity or where the fire performance specification matters.

Polyurethane foam: Injected as a liquid that expands and sets. Fast-setting and suits irregular or narrower cavities. Less commonly used but effective in the right conditions.

The contractor recommends the correct material based on the cavity survey results. You do not choose the material yourself. What matters is that the contractor is SEAI-registered and uses a BBA-certified or NSAI-certified product.

Does Cavity Wall Insulation Cause Damp?

This is the most common concern homeowners raise and it deserves a direct answer.

Correctly installed cavity wall insulation does not cause damp.

The risk of damp is associated with poorly installed insulation in homes that already have existing damp problems. The cavity survey identifies damp issues before installation begins. If the installer finds moisture in the cavity, they will not proceed until the source is identified and resolved.

Correctly filled cavities actually reduce the risk of condensation on interior walls by keeping wall surfaces warmer. Cold, empty cavities allow the inner leaf to get cold, which can cause condensation on internal wall surfaces. Insulating the cavity reduces this effect.

If your home has existing damp problems from other sources such as gutters, roof leaks or rising damp, those need to be addressed before insulation. A good installer will tell you this at survey stage.

The Heat Pump Connection: Why Cavity Walls Come First

This is the strategic reason to prioritise cavity wall insulation before most other upgrades.

The SEAI heat pump grant requires your home to have a Heat Loss Indicator (HLI) of 2.3 W/K·m² or lower. The HLI measures how fast heat escapes from your home through its walls, roof and floor. A lower HLI means less heat loss and a more efficient heat pump.

Most 3-bed semi-D homes with uninsulated cavity walls have an HLI above 2.3. After cavity wall insulation, many of these homes drop below the 2.3 threshold. Combined with attic insulation already in place, cavity wall insulation often makes the difference between being heat pump eligible and not.

This double wall approach makes your home significantly warmer and heat pump ready.

The correct sequence for most Irish semi-D homes is: attic insulation first, then cavity wall insulation, then apply for heat pump grant. Both insulation measures are quicker and cheaper than a heat pump installation, and together they unlock the largest grant available.

Full guide to SEAI heat pump grant Ireland 2026. Check your home's grant eligibility.

Second Wall Measure: What Changed in March 2026

From 2 March 2026, homeowners who previously received a grant for cavity or internal wall insulation can now apply for a second wall insulation measure.

Here is exactly how the new rule works.

Previously claimed	Can now also claim
Cavity wall insulation	Internal wall insulation OR external wall insulation
Internal wall insulation	External wall insulation only
External wall insulation	No second measure available

This matters for two groups of homeowners.

First, homes that had cavity wall insulation installed years ago but are now planning a heat pump and want to maximise thermal performance. Adding external wall insulation on top of existing cavity fill pushes the HLI down further.

Second, homes where the cavity was only partially suitable. Some older homes have a cavity on three walls but a solid wall on the fourth. Cavity fill covers the three walls, then internal or external insulation covers the fourth.

The second wall measure uses a separate grant application. You cannot combine both in one application.

What the Installation Involves

Most homeowners are surprised at how quick and undisruptive cavity wall insulation is.

Cavity fill typically takes half a day. The installer drills holes in the outer leaf, injects insulation, and makes good.

Here is the full process for a standard semi-D.

The installer drills holes of 12mm to 18mm diameter in the outer leaf of the wall, spaced every 600mm in a diagonal pattern. This covers all external cavity walls of the house.

Insulation material is injected through each hole using a hose connected to a blowing machine. The machine forces material through the holes until the cavity is completely filled.

Once a section is filled, the holes are plugged with mortar that is colour-matched to your existing exterior finish where possible. The plugs are small and become almost invisible after drying.

There is no work inside the house. You do not need to clear rooms, move furniture or leave the property. The exterior finish is the only thing affected.

After the installation, the contractor submits a completion certificate to SEAI. You submit a request for payment. SEAI processes and pays the grant within a few weeks.

Real Costs After the Grant

Cavity wall insulation for a 3-bed semi-D costs €800 to €1,500 before the grant. After the SEAI grant of €1,200, the net cost is typically €0 to €300.

For a detached house, costs run €1,500 to €2,500 before the grant. After the €1,800 grant, the net cost is €0 to €700.

For homeowners on qualifying welfare payments, the enhanced grant of €2,300 covers the full cost for most property types.

Property type	Typical cost	Standard grant	Net cost
Detached house	€1,500 to €2,500	€1,800	€0 to €700
Semi-D or end-terrace	€800 to €1,500	€1,200	€0 to €300
Mid-terrace	€600 to €1,000	€800	€0 to €200
Apartment	€500 to €800	€700	€0 to €100

Always get three written quotes from SEAI-registered contractors. Prices vary between contractors. The grant amount is fixed, so a lower quote means a lower net cost to you.

For Landlords: A Near-Zero Net Cost

Landlords qualify for the same SEAI cavity wall insulation grant as owner-occupiers.

On top of the grant, landlords can deduct the cost of retrofit works from their rental income. Landlords can deduct the lesser of €10,000 or the actual amount incurred on retrofitting works (net of the SEAI grant amount) from their rental income. The limit increases to a maximum of three properties for works done from 2026 to 2028.

For a typical semi-D rental property: cavity wall insulation costs €1,200, SEAI grant covers €1,200. Net cost to the landlord is €0. If the cost exceeds the grant, the difference is deducted from rental income.

This makes cavity wall insulation one of the most compelling upgrades for the private rented sector in 2026.

How to Apply

Step 1: Get a BER assessment. A current BER helps you understand your home's starting point and which upgrades will have the biggest impact. A BER assessment costs €150 to €300. The SEAI grant covers €50 of this cost (€280 if you receive qualifying welfare payments). Find a registered assessor at ndber.seai.ie.

Step 2: Find an SEAI-registered cavity wall contractor. Not all insulation contractors are SEAI-registered. Check the contractor register at hes.seai.ie before making contact. Get at least three quotes. The SEAI registered contractors guide explains what to look for.

Step 3: Get the cavity survey done. Your chosen contractor visits and surveys the cavity walls. This is typically free. They confirm suitability and provide a written quotation.

Step 4: Apply for SEAI grant approval. Apply at hes.seai.ie before any work starts. You need your MPRN, property details and the contractor's SEAI registration number.

Step 5: Receive written approval and proceed. Do not allow any work to start before SEAI written approval arrives. Works started before approval permanently disqualify the grant with no exceptions.

Step 6: Installation and grant payment. Installation takes half a day. After completion, your contractor submits paperwork to SEAI. Grant payment arrives within a few weeks.

Frequently Asked Questions

Can cavity wall insulation cause damp?

No, when installed correctly by a registered contractor. The cavity survey identifies any existing damp before work begins. Installers will not proceed if the cavity already has moisture issues.

How long does cavity wall insulation last?

EPS bead and mineral wool cavity fill typically last 25 years or more. Properly installed cavity fill does not settle or degrade under normal conditions.

Does it affect my home's appearance?

The drilled holes are made good with mortar plugs after installation. For rendered homes, the plugs are colour-matched and become virtually invisible. For brick homes, small circular mortar plugs will be visible on close inspection but are not obvious from a normal viewing distance.

Can I get this grant and the windows grant?

Yes. The cavity wall insulation grant and the windows and doors grant are separate applications that can be claimed on the same home. Cavity wall insulation can also help your home meet the HLI requirement for the windows grant.

Do I need cavity wall insulation before a heat pump?

Not technically required, but strongly recommended. Cavity wall insulation reduces your HLI and makes your home more heat pump efficient. Many homes with uninsulated cavities do not meet the HLI threshold of 2.3 required for the heat pump grant. Get insulation in place first, confirm your HLI with a BER assessment, then apply for the heat pump.

Can I do cavity walls and attic insulation at the same time?

Yes. Both grants can be applied for and completed at the same time. This is the recommended approach if neither measure has been done. Together, attic and cavity wall insulation deliver the most significant HLI reduction for most Irish homes.

External Sources

• SEAI: Wall insulation grants
• Apply at hes.seai.ie
• Government press release: January 2026 grant announcement
• Citizens Information: Home energy grants

All grant amounts verified against seai.ie May 2026. SEAI scheme rules can change. Always verify current eligibility and amounts at seai.ie before starting any works or making any payment.